/**
 * @author       Richard Davey <rich@photonstorm.com>
 * @copyright    2020 Photon Storm Ltd.
 * @license      {@link https://opensource.org/licenses/MIT|MIT License}
 */

 var Class = require('../../utils/Class');
 var CONST = require('../const');
 var File = require('../File');
 var FileTypesManager = require('../FileTypesManager');
 var GetFastValue = require('../../utils/object/GetFastValue');
 var IsPlainObject = require('../../utils/object/IsPlainObject');
 var Shader = require('../../display/shader/BaseShader');
 
 /**
  * @classdesc
  * A single GLSL File suitable for loading by the Loader.
  *
  * These are created when you use the Phaser.Loader.LoaderPlugin#glsl method and are not typically created directly.
  *
  * For documentation about what all the arguments and configuration options mean please see Phaser.Loader.LoaderPlugin#glsl.
  *
  * @class GLSLFile
  * @extends Phaser.Loader.File
  * @memberof Phaser.Loader.FileTypes
  * @constructor
  * @since 3.0.0
  *
  * @param {Phaser.Loader.LoaderPlugin} loader - A reference to the Loader that is responsible for this file.
  * @param {(string|Phaser.Types.Loader.FileTypes.GLSLFileConfig)} key - The key to use for this file, or a file configuration object.
  * @param {string} [url] - The absolute or relative URL to load this file from. If undefined or `null` it will be set to `<key>.txt`, i.e. if `key` was "alien" then the URL will be "alien.txt".
  * @param {string} [shaderType='fragment'] - The type of shader. Either `fragment` for a fragment shader, or `vertex` for a vertex shader. This is ignored if you load a shader bundle.
  * @param {Phaser.Types.Loader.XHRSettingsObject} [xhrSettings] - Extra XHR Settings specifically for this file.
  */
 var GLSLFile = new Class({
 
     Extends: File,
 
     initialize:
 
     function GLSLFile (loader, key, url, shaderType, xhrSettings)
     {
         var extension = 'glsl';
 
         if (IsPlainObject(key))
         {
             var config = key;
 
             key = GetFastValue(config, 'key');
             url = GetFastValue(config, 'url');
             shaderType = GetFastValue(config, 'shaderType', 'fragment');
             xhrSettings = GetFastValue(config, 'xhrSettings');
             extension = GetFastValue(config, 'extension', extension);
         }
         else if (shaderType === undefined)
         {
             shaderType = 'fragment';
         }
 
         var fileConfig = {
             type: 'glsl',
             cache: loader.cacheManager.shader,
             extension: extension,
             responseType: 'text',
             key: key,
             url: url,
             config: {
                 shaderType: shaderType
             },
             xhrSettings: xhrSettings
         };
 
         File.call(this, loader, fileConfig);
     },
 
     /**
      * Called automatically by Loader.nextFile.
      * This method controls what extra work this File does with its loaded data.
      *
      * @method Phaser.Loader.FileTypes.GLSLFile#onProcess
      * @since 3.7.0
      */
     onProcess: function ()
     {
         this.state = CONST.FILE_PROCESSING;
 
         this.data = this.xhrLoader.responseText;
 
         this.onProcessComplete();
     },
 
     /**
      * Adds this file to its target cache upon successful loading and processing.
      *
      * @method Phaser.Loader.FileTypes.GLSLFile#addToCache
      * @since 3.17.0
      */
     addToCache: function ()
     {
         var data = this.data.split('\n');
 
         //  Check to see if this is a shader bundle, or raw glsl file.
         var block = this.extractBlock(data, 0);
 
         if (block)
         {
             while (block)
             {
                 var key = this.getShaderName(block.header);
                 var shaderType = this.getShaderType(block.header);
                 var uniforms = this.getShaderUniforms(block.header);
                 var shaderSrc = block.shader;
 
                 if (this.cache.has(key))
                 {
                     var shader = this.cache.get(key);
 
                     if (shaderType === 'fragment')
                     {
                         shader.fragmentSrc = shaderSrc;
                     }
                     else
                     {
                         shader.vertexSrc = shaderSrc;
                     }
 
                     if (!shader.uniforms)
                     {
                         shader.uniforms = uniforms;
                     }
                 }
                 else if (shaderType === 'fragment')
                 {
                     this.cache.add(key, new Shader(key, shaderSrc, '', uniforms));
                 }
                 else
                 {
                     this.cache.add(key, new Shader(key, '', shaderSrc, uniforms));
                 }
 
                 block = this.extractBlock(data, block.offset);
             }
         }
         else if (this.config.shaderType === 'fragment')
         {
             //  Single shader
             this.cache.add(this.key, new Shader(this.key, this.data));
         }
         else
         {
             this.cache.add(this.key, new Shader(this.key, '', this.data));
         }
     },
 
     /**
      * Returns the name of the shader from the header block.
      *
      * @method Phaser.Loader.FileTypes.GLSLFile#getShaderName
      * @since 3.17.0
      *
      * @param {string[]} headerSource - The header data.
      *
      * @return {string} The shader name.
      */
     getShaderName: function (headerSource)
     {
         for (var i = 0; i < headerSource.length; i++)
         {
             var line = headerSource[i].trim();
 
             if (line.substring(0, 5) === 'name:')
             {
                 return line.substring(5).trim();
             }
         }
 
         return this.key;
     },
 
     /**
      * Returns the type of the shader from the header block.
      *
      * @method Phaser.Loader.FileTypes.GLSLFile#getShaderType
      * @since 3.17.0
      *
      * @param {string[]} headerSource - The header data.
      *
      * @return {string} The shader type. Either 'fragment' or 'vertex'.
      */
     getShaderType: function (headerSource)
     {
         for (var i = 0; i < headerSource.length; i++)
         {
             var line = headerSource[i].trim();
 
             if (line.substring(0, 5) === 'type:')
             {
                 return line.substring(5).trim();
             }
         }
 
         return this.config.shaderType;
     },
 
     /**
      * Returns the shader uniforms from the header block.
      *
      * @method Phaser.Loader.FileTypes.GLSLFile#getShaderUniforms
      * @since 3.17.0
      *
      * @param {string[]} headerSource - The header data.
      *
      * @return {any} The shader uniforms object.
      */
     getShaderUniforms: function (headerSource)
     {
         var uniforms = {};
 
         for (var i = 0; i < headerSource.length; i++)
         {
             var line = headerSource[i].trim();
 
             if (line.substring(0, 8) === 'uniform.')
             {
                 var pos = line.indexOf(':');
 
                 if (pos)
                 {
                     var key = line.substring(8, pos);
 
                     try
                     {
                         uniforms[key] = JSON.parse(line.substring(pos + 1));
                     }
                     catch (e)
                     {
                         console.warn('Invalid uniform JSON: ' + key);
                     }
                 }
             }
         }
 
         return uniforms;
     },
 
     /**
      * Processes the shader file and extracts the relevant data.
      *
      * @method Phaser.Loader.FileTypes.GLSLFile#extractBlock
      * @private
      * @since 3.17.0
      *
      * @param {string[]} data - The array of shader data to process.
      * @param {number} offset - The offset to start processing from.
      *
      * @return {any} The processed shader block, or null.
      */
     extractBlock: function (data, offset)
     {
         var headerStart = -1;
         var headerEnd = -1;
         var blockEnd = -1;
         var headerOpen = false;
         var captureSource = false;
         var headerSource = [];
         var shaderSource = [];
 
         for (var i = offset; i < data.length; i++)
         {
             var line = data[i].trim();
 
             if (line === '---')
             {
                 if (headerStart === -1)
                 {
                     headerStart = i;
                     headerOpen = true;
                 }
                 else if (headerOpen)
                 {
                     headerEnd = i;
                     headerOpen = false;
                     captureSource = true;
                 }
                 else
                 {
                     //  We've hit another --- delimiter, break out
                     captureSource = false;
                     break;
                 }
             }
             else if (headerOpen)
             {
                 headerSource.push(line);
             }
             else if (captureSource)
             {
                 shaderSource.push(line);
                 blockEnd = i;
             }
         }
 
         if (!headerOpen && headerEnd !== -1)
         {
             return { header: headerSource, shader: shaderSource.join('\n'), offset: blockEnd };
         }
         else
         {
             return null;
         }
     }
 
 });
 
 /**
  * Adds a GLSL file, or array of GLSL files, to the current load queue.
  * In Phaser 3 GLSL files are just plain Text files at the current moment in time.
  *
  * You can call this method from within your Scene's `preload`, along with any other files you wish to load:
  *
  * ```javascript
  * function preload ()
  * {
  *     this.load.glsl('plasma', 'shaders/Plasma.glsl');
  * }
  * ```
  *
  * The file is **not** loaded right away. It is added to a queue ready to be loaded either when the loader starts,
  * or if it's already running, when the next free load slot becomes available. This happens automatically if you
  * are calling this from within the Scene's `preload` method, or a related callback. Because the file is queued
  * it means you cannot use the file immediately after calling this method, but must wait for the file to complete.
  * The typical flow for a Phaser Scene is that you load assets in the Scene's `preload` method and then when the
  * Scene's `create` method is called you are guaranteed that all of those assets are ready for use and have been
  * loaded.
  *
  * The key must be a unique String. It is used to add the file to the global Shader Cache upon a successful load.
  * The key should be unique both in terms of files being loaded and files already present in the Shader Cache.
  * Loading a file using a key that is already taken will result in a warning. If you wish to replace an existing file
  * then remove it from the Shader Cache first, before loading a new one.
  *
  * Instead of passing arguments you can pass a configuration object, such as:
  *
  * ```javascript
  * this.load.glsl({
  *     key: 'plasma',
  *     shaderType: 'fragment',
  *     url: 'shaders/Plasma.glsl'
  * });
  * ```
  *
  * See the documentation for `Phaser.Types.Loader.FileTypes.GLSLFileConfig` for more details.
  *
  * Once the file has finished loading you can access it from its Cache using its key:
  *
  * ```javascript
  * this.load.glsl('plasma', 'shaders/Plasma.glsl');
  * // and later in your game ...
  * var data = this.cache.shader.get('plasma');
  * ```
  *
  * If you have specified a prefix in the loader, via `Loader.setPrefix` then this value will be prepended to this files
  * key. For example, if the prefix was `FX.` and the key was `Plasma` the final key will be `FX.Plasma` and
  * this is what you would use to retrieve the text from the Shader Cache.
  *
  * The URL can be relative or absolute. If the URL is relative the `Loader.baseURL` and `Loader.path` values will be prepended to it.
  *
  * If the URL isn't specified the Loader will take the key and create a filename from that. For example if the key is "plasma"
  * and no URL is given then the Loader will set the URL to be "plasma.glsl". It will always add `.glsl` as the extension, although
  * this can be overridden if using an object instead of method arguments. If you do not desire this action then provide a URL.
  *
  * Note: The ability to load this type of file will only be available if the GLSL File type has been built into Phaser.
  * It is available in the default build but can be excluded from custom builds.
  *
  * @method Phaser.Loader.LoaderPlugin#glsl
  * @fires Phaser.Loader.LoaderPlugin#ADD
  * @since 3.0.0
  *
  * @param {(string|Phaser.Types.Loader.FileTypes.GLSLFileConfig|Phaser.Types.Loader.FileTypes.GLSLFileConfig[])} key - The key to use for this file, or a file configuration object, or array of them.
  * @param {string} [url] - The absolute or relative URL to load this file from. If undefined or `null` it will be set to `<key>.glsl`, i.e. if `key` was "alien" then the URL will be "alien.glsl".
  * @param {string} [shaderType='fragment'] - The type of shader. Either `fragment` for a fragment shader, or `vertex` for a vertex shader. This is ignored if you load a shader bundle.
  * @param {Phaser.Types.Loader.XHRSettingsObject} [xhrSettings] - An XHR Settings configuration object. Used in replacement of the Loaders default XHR Settings.
  *
  * @return {this} The Loader instance.
  */
 FileTypesManager.register('glsl', function (key, url, shaderType, xhrSettings)
 {
     if (Array.isArray(key))
     {
         for (var i = 0; i < key.length; i++)
         {
             //  If it's an array it has to be an array of Objects, so we get everything out of the 'key' object
             this.addFile(new GLSLFile(this, key[i]));
         }
     }
     else
     {
         this.addFile(new GLSLFile(this, key, url, shaderType, xhrSettings));
     }
 
     return this;
 });
 
 module.exports = GLSLFile;
 